The present invention relates to a hot gas machine which includes low-temperature, middle-temperature and high-temperature heat sources, which causes a working medium to absorb the heat from the low-temperature heat source and from the high-temperature heat source, and which discharges the absorbed heat to the middle-temperature heat source.
One of the basic machines which comprises low-temperature, middle-temperature and high-temperature heat sources and discharges the absorbed heat to the middle-temperature heat source is a Vuilleumier (VM) cycle machine as disclosed in U.S. Pat. No. 1,275,507.
In general, a hot gas machine has two displacers for displacing a working medium, that is, a high-temperature displacer and a low-temperature displacer, and is divided into a high temperature portion and a low temperature portion with which the displacers are respectively associated. That is, in both the high temperature portion and the low temperature portion, the working medium is displaced by the operation of the displacers. The volume of a "working chamber" changes as the gas is displaced by a displacer. The high temperature portion and the low temperature portion each has two working chambers, one of which is under a temperature substantially equal to that of the middle-temperature heat source and will be hereinafter referred to as "a middle temperature chamber". Similarly, the working chamber under a temperature equal to that of the high-temperature heat source and the working chamber under a temperature equal to that of the low-temperature heat source will be referred to as "a high temperature chamber" and "a low temperature chamber", respectively.
The work associated with these working chambers, due to a change in volume and pressure of the medium occupying the working space (entire space of the machine), includes expansion of the medium in the high temperature chamber, compression of the medium in the middle temperature chamber of the high temperature portion, expansion of the medium in the low temperature chamber, and compression of the medium in the middle temperature chamber of the low temperature portion.
In the conventional hot gas Vuilleumier (VM) machine described above, heat is merely transferred from among the three heat sources and the gas displacement volumes of the high temperature portion and the low temperature portion are equal to each other. Thus, the absolute volumes of gas expanded and compressed in the high temperature portion are equal to each other, and the absolute volumes of gas expanded and compressed in the low temperature portion are equal to each other for given strokes of the displacers, respectively. In the practical machine, rods are provided to drive the displacers as shown in Japanese Patent Publication (unexamined) No. 63-311050.
The diameter of the rod connected to the high temperature displacer is different from that of the rod connected to the low temperature displacer so that total volume of the high and low temperature portions varies and only a shaft output is increased by the varied total volume and the pressure change of the working medium (gas) sealed therein.